During normal operation of a conveyor belt, the ends of the belt may be spliced together to form a continuous belt. The belt ends are connected together in such a manner that the continuous belt so formed is in tension throughout its length as it extends about rollers which define the continuous path of travel of the belt.
Conveyor belts have some elasticity, so that when pulled upon they stretch and become slightly elongated. The belts are tensioned about end rollers and in particular the drive rollers which engage and drive the endless belt. Upon rupture or tearing of the belt, the tension in the belt causes the portions of the belt on either side of the rupture to be pulled apart. Current methods and apparatus for re-connecting the belt ends at the point of belt rupture suffer numerous shortcomings. In order to splice the ends of the belt in the field, a portable belt gripping and tension device is brought to the location on the conveyor at which the rupture is located.
It is desirable to effect re-connecting of the belt ends together while the belt ends are flaccid, so that it is not necessary to deal with the forces tending to separate the belt ends from one another while attempting to connect the belt ends.
Known portable belt clamping and stretching devices include a pair of clamping plates together on either side of the belt in proximity with both of the respective belt ends for clamping the belt ends, and pulling the clamped belt ends toward one another. This stretches the belt and places the belt into tension over its length except over the end portions of the belt which are situated between the clamps, which end portions are slacked or flaccid, thereby allowing a splicing of the belt ends to one another in a tension-free environment.
It is known to utilize clamping jaws which close together about the clamping plates, to press the plates together, as the clamping jaws are pulled upon to pull the belt ends toward one another. The clamping force which the clamping jaws exert upon the clamping plates is directly proportional to the pulling force pulling the belt ends toward one another. That is, upon pulling on the clamping jaws to pull the belt ends toward one another, the clamping plates above and below the respective belt ends move closer toward one another to clamp the belt therebetween. This arrangement suffers numerous shortcomings, most of which are associated with slippage of the belt with respect to the clamping plates, as discussed below.
One cause of the undesirable slippage between the belt and the clamping plates is due to the fact that upon initial pulling on the clamping jaws to pull the belt ends toward one another, the clamping jaws and their associated clamping plates are pulled toward one another prior to the clamping plates having attained a sufficient clamping force on the respective belt ends. That is, when the clamping jaws are initially pulled upon, they do not tightly clamp the clamping plates to the belt. Hence, during the initial pulling, as the clamping plates are just beginning to clamp down on the belt ends, the clamping jaws and their associated clamping plates are being pulled toward one another. The clamping plates thus slip or slide across the belt until they are closed together sufficiently by the clamping jaws to prevent further slippage of the belt from between the clamping plates.
The initial slippage of the belt through the clamping plates is undesirable since it precludes precise positioning of the clamping plates at the belt ends, and such slippage may be a safety hazard. The initial slippage of the belt is also undesirable since this requires the operator to pull the belt ends further than he would otherwise have to in order to stretch the belt sufficiently. That is, chains or other pulling members interconnect the clamping jaws of opposite belt ends and shortening the length of the chains pulls the belt ends together. Thus, there is a need for a belt clamping apparatus which prevents initial slippage of the belt when the belt ends are initially pulled toward one another.
Another cause of slippage with current belt clamping and pulling apparatus is that the flat clamping plates, which are currently used to press together on opposite sides of the belt to grip the belt, do not provide a good gripping of belts of various widths between the flat plates. The clamping jaws which press the flat plates together are positioned at the outer ends of the plates to accommodate both narrow and wide belts between the spaced clamping jaws. Hence, for all but the widest belts, the clamping jaws are spaced outwardly from the sides of the belt. Thus, when the respective ends of the plates are pressed toward one another, the plates bow outwardly from their center. That is, since the clamping jaws are positioned outwardly of the sides of the belt, the clamping plates deflect the ends of the clamping plates toward each other and tend to raise or bow the central portions of the clamping plates over a substantial, central portion of the belt. Accordingly, the sides of the belt are clamped with high clamping forces with the central portions of the clamping plates receiving reduced clamping forces. There is a need for belt clamping members which provide a more uniform gripping of the belt across its width.